// Given a positive integer num consisting only of digits 6 and 9.
//
// Return the maximum number you can get by changing at most one digit (6 becomes 9, and 9 becomes 6).
//
//  
// Example 1:
//
//
// Input: num = 9669
// Output: 9969
// Explanation: 
// Changing the first digit results in 6669.
// Changing the second digit results in 9969.
// Changing the third digit results in 9699.
// Changing the fourth digit results in 9666. 
// The maximum number is 9969.
//
//
// Example 2:
//
//
// Input: num = 9996
// Output: 9999
// Explanation: Changing the last digit 6 to 9 results in the maximum number.
//
// Example 3:
//
//
// Input: num = 9999
// Output: 9999
// Explanation: It is better not to apply any change.
//
//  
// Constraints:
//
//
// 	1 <= num <= 10^4
// 	num's digits are 6 or 9.
//


class Solution {
    public int maximum69Number (int num) {
        return Integer.parseInt(String.valueOf(num)
                .replaceFirst("6","9"));
    }
}
